It is well known to provide pressure relieving mattresses for hospital beds to reduce the number and severity of pressure sores experienced by immobile patents. Typically such mattresses fall into two classes. Those which comprise foam-based products, which incorporate a profiling on the upper face, and those which are inflatable and work by progressive inflation of successive cells.
Over the years profiling beds, where the head, trunk, and leg portions can be articulated relative to one another, have become more and more popular but mattress design has not satisfactorily coped with these beds.
It is well known that shear and friction are significant contributory factors towards the development of pressure ulcers and, as can be seen in FIG. 1, when a user is present and the bed is profiled, the user is subjected to excessive compression, shear and friction forces as schematically indicated at A-E. The body of the user is effectively pushed along the mattress each time the bed is profiled. In some instances, this movement can be as much as seven or eight inches.